Iodine 131 is normatively written as iodine-131, which is a radioactive therapeutic drug commonly used in the treatment of hyperthyroidism and thyroid cancer. Iodine-131 can cause radioactive contamination to family members through direct radiation or contact or inhalation into the body, which may damage the thyroid gland and lead to short-term inability to conceive or have children.1. Damage to the thyroid gland: Iodine-131 can produce radiation. When patients taking radioactive iodine come into contact with their family members, the rays emitted by radioactive iodine may cause damage to the thyroid gland of their family members, causing thyroid dysfunction or thyroiditis. In particular, radioactive iodine excreted through urine and faeces has a longer radiation range and requires extra attention. 2. No pregnancy or childbirth in the short term: Women should not get pregnant until at least 6-12 months after iodine-131 treatment because their ovaries will be damaged by the radioactivity. Men will experience a decrease in sperm count and temporary sterility for about 2 years. Therefore couples who have plans to have children will have to put them on hold. In conclusion, after drinking Iodine-131 one should avoid contact with other people, especially pregnant women and children, in order to reduce the dose of radiation to which others are exposed. It is also recommended to share meals for 2 weeks after drinking iodine-131 to avoid contamination of food and utensils, to drink more water and urinate more often, to use a toilet to avoid contamination by urine splashing, and to flush the toilet more than 2 times after defecation.